Overcurrent protection devices are used to protect electrical installations and delicate equipment against excessive currents. The more expensive, repeatable type devices employ monitoring equipment to detect when the current exceeds a prescribed threshold. This equipment is adapted to activate a switching mechanism which is in line with the conductor drawing the excessive current or alternately is adapted to cutout the voltage or current source supplying the load.
In addition to this relatively expensive manner it is also known to insert into the circuits to be protected, fuses whose fusible link is melted by the overcurrent until opened. In contrast to overcurrent protection switches, fuses can be used only once however.
Another known design for overcurrent protection devices is described in U.S. Pat. No. 3,613,039. Therein is described a vacuum switching vessel which comprises two electrodes which face each other at a distance and between which fusible links are disposed. An overcurrent causes these fusible links to evaporate, whereby a metal vapor arc is ignited between the electrodes. This arc is extinguished after a short time in a manner similar as in the known vacuum switching vessels. However, protective devices of this kind, too, can be used only once. It is therefore an object of this invention to provide an overcurrent protection device which can be used several times but is of simpler design and requires less space than the known overcurrent protection switches. It is another object of this invention to provide an overcurrent protection device which is fast responding and which can be automatically reset.